Opto module

ABSTRACT

An electro-optical circuit includes optical sending and receiving components for transforming an electrical output signal to an optical output signal, and for transforming a received optical signal to an electrical input signal, respectively. The electro-optical circuit forms a module with an electro magnetically shielded case which contains the optical sending and receiving components and connection devices for an optical conductor on which the outgoing and received optical signals are transmitted. A two-sided printed circuit arrangement carries a sender for the electrical output signal and a receiver for the electrical input signal located shielded from each other on one side each by means of an electrically conducting shielding. The shielding is in connection with the case for forming three Faraday&#39;s cages, one for the sender, one for the receiver and one formed of the case in its entirety.

This application is a continuation of International Application No.PCT/SE96/01035, which was filed on Aug. 21, 1996, which designated theUnited States, and which is expressly incorporated here by reference.

BACKGROUND

The present invention relates to an arrangement in an electro-opticcircuit that comprises optic sender and receiver components fortransforming an electric output signal to an outgoing optic signal andfor transforming a received optic signal to an electric input signal,respectively, connection means for an opto conductor on which theoutgoing and received optic signals are transmitted, a sender for theelectric output signal, and a receiver for the electric input signal.

Electro-optic circuits of this kind are used e.g. located on a printedcircuit card in a telecommunication switch. Each circuit card carries aplurality of such electro-optic circuits and in the switch one or morecabinets can contain a plurality of shielded card magazines, each ofwhich contains a plurality of such circuit cards. For increasing theinsensitivity towards EMC, i.e. electromagnetical disturbance radiation,senders and receivers are conventionally located far in on the card asseen from its edge located at an outer cabinet wall, below denominatedcard front. On the card front there are seated a number of connectiondevices for connecting an outer opto conductor to two opto conductorsleading to the sender and receiver, respectively, of a correspondingsender/receiver pair. For minimizing the risk for interference betweensender and receiver of each sender/receiver pair the sender and thereceiver are furthermore located remote from each other on the card.

This distribution of the components of the electro-optic circuitcounteracts a striving for a more compact architecture of switches ofthe just described type, while saving or further improving theinsensitiveness for EMC, as well as ESD, i.e. electrostaticaldischarges.

SUMMARY

One object of the invention is to provide an electro-optic circuit ofthe kind defined by way of introduction that is characterized by a verycompact design and great insensitiveness to EMC and ESD and thereby canbe mounted at the card front as a unit.

This object has been achieved in that, in the arrangement of the kinddefined by way of introduction, the electro-optic circuit forms a modulewith an electromagnetically shielded housing that contains said opticalsender and receiver components and said connection means, and atwo-sided printed circuit arrangement that carries the sender and thereceiver located shielded from each other on one side each by means ofan electrically conducting shielding that is in connection with thehousing for forming three Faraday's cages, one for the sender, one forthe receiver and one formed of the housing in its entirety.

Embodiments of the invention have then received the features stated inrespective subclaims.

DESCRIPTION OF DRAWINGS

The invention will now be described more closely with reference to theattached drawings, on which

FIG. 1 is a perspective view of a housing for an electro-optic circuitmounted on a mother printed circuit card,

FIG. 2 shows an exploded view of the housing shown in FIG. 1 with theparts thereof as well as components enclosed thereby being shown inperspective,

FIG. 3 shows a perspective view of a contact spring module according tothe invention used in the housing and intended to be used betweendifferent elements, forming parts of the housing according to FIG. 1, aprinted circuit card introduced in the housing and the mother card,

FIGS. 4 and 5 show sections in the direction of arrows IV--IV in FIG. 3through the contact spring module for illustrating cooperation thereofwith the elements shown in FIG. 3,

FIG. 6 shows a perspective view of a housing for a contact means,

FIG. 7 shows an exploded view of the housing shown in FIG. 6 with theparts thereof as well as components enclosed therein in perspective,

FIG. 8 shows a perspective view of a component enclosed in the housingaccording to FIGS. 6 and 7 and turned 90° anti-clockwise in the sameplane as the corresponding perspective view in FIG. 7,

FIG. 9 shows a perspective view of the same component as in FIG. 8,although turned 180° about a length axis with respect to thecorresponding perspective view in FIG. 7,

FIG. 10 shows a longitudinal section of another component enclosed inthe housing according to FIG. 7.

DETAILED DESCRIPTION

FIG. 1 shows the housing for an electro-optic circuit according to theinvention, generally designated 2, and mounted on a mother card 4. Thehousing 2, the design of which appears more closely from FIG. 2,contains connection means in the form of a housing 6 with a receivingtube 7 for receiving one end of an opto conductor. The opto conductor iskept fixedly by a connection device generally designated 8 and receivedin an opening in a guiding-in part generally designated 9. Theconnection device 8 will be described more closely further on.

The housing 6 contains an electro-optic component not shown andcomprising optic sender and receiver component parts for transforming anelectric output signal to an outgoing optic signal, and for transforminga received opto signal to an electric input signal, respectively. Theoptic sender and receiver component parts can be combined into a unit,e.g. Duplex-2 from ABB HAFO, that admits use of one single opto fibrefor transfer in both directions to and from the electro-optic component.

The housing 2 furthermore encloses a printed circuit card arrangement 10on which the housing 6 is attached. The printed circuit card arrangement10 is in the form of a sender/receiver printed circuit card 10 and ishenceforth, for the sake of simplicity, denominated "printed circuitcard" or, alternatively, "sender/receiver printed circuit card", despitethe fact that it, as described below, can consist of a sandwich of twoprinted circuit cards. The printed circuit card 10 on one side carries asender circuit for the electric output signal and on the other side areceiver circuit for the electric input signal. The circuits areindicated for the upper side of the card at 12 and for the lower side ofthe card with an arrow 13, but are not shown more closely for the rest.The card 10 furthermore carries connections, not shown, between inputsand outputs of the sender and receiver circuits, respectively, on theone hand, and connection pins 14 on the other hand, that extend throughthe housing to the outside thereof for connection to outer circuits onthe mother card 4.

The housing 2 has a lower part 16 and an upper part 18, both metallic,comprising each one half 9a and 9b, respectively, of the guiding in part9. Between the lower part 16 and the upper part 18, the sender/receiverprinted circuit card 10 is located, the housing containing contactmeans, described more closely below, between the parts of the housingand between the housing and grounding parts of the sender/receiverprinted circuit card 10 and the outer card 4, respectively. As willappear more clearly below said grounding parts of the mother card formpart of a metallic layer applied in the card in parallel with andbetween the two sides of the printed circuit card. The printed circuitcard 10 can then consist of one single printed circuit card in which themetallic layer is formed by an integrated conducting layer between thesides of the card. The printed circuit card 10 can, however, also besandwich-like composed of two printed circuit cards connected togetherside to side via the metallic layer. The metallic layer can also includea magnetic material, e.g. in the form of a nickel plate for shieldingagainst inductive cross-induction. By the design of the housing 2 justdescribed it forms three Faraday's cages. Two of the cages each encloseone of the sender and receiver circuits 12 and 13, respectively, oneconsisting of the lower part 16 of the housing and the metallic layer ofthe printed circuit card 10, and the other one consisting of the upperpart 18 of the housing and the metallic layer of the printed circuitcard. The third cage is the housing 2 in its entirety.

The above mentioned contact means consist of a number of longitudinalspring means 20 along the sides of the housing parts 16 and 18. Eachspring means 20 is made in one piece and comprises a number of contactpoints for the sender/receiver printed circuit card 10, a number ofcontact points for the housing lower part 16, a number of contact pointsfor the housing upper part 18, and a number of contact points for themother card 4.

Each spring means has a first essentially rib-shaped web part 22extending along the longitudinal direction of the spring means. A secondweb part 24 extends along and at a distance from the first web part 22and is connected thereto by means of arcuate connection pieces 26extending from a first side edge 28 of the first web part to a nearbyfirst side edge 30 of the second web part. First contact tongues 32 arebent away from the first side edge 30 of the second web part in adirection towards the first web part 22 and end between the planes ofthe two web parts. Second contact tongues 34 are arcuately bent awayfrom the first side edge 28 of the first web part 22 in a directiontowards the second web part 24 and end outside the plane of the secondweb part. Each one of the first and one of the second contact tongues 32and 34, respectively, are arranged pairwise in the spaces between thearcuate connection pieces 26. Third contact tongues 36 are bent awayfrom the second side edge of the first web part 22 in a directionoutwardly from the two web parts. Each one of the third contact tongues36 has an inner leg 38 bent away from the first web part 22 and an outerleg 40 connected thereto and bent away from the inner leg for forming anacute angle between the two legs.

The web part 22 extends between the inside of a side wall 42 standing upfrom the bottom wall of the lower part 16 and an opposite side edge 44of the sender/receiver printed circuit card 10. The web part 24 extendsbetween the outside of the side wall 42 of the lower part and the insideof a side wall 46 extending downwardly from the upper wall of the upperpart 18. The contact tongues 32 are located in contact with the outsideof the side wall 42 of the lower part 16. The contact tongues 34 arelocated in contact with the inside of the side wall 46 of the housingupper part 18.

The contact tongues 36 extend between and abut grounding parts, notshown, on the lower side of the sender/receiver printed circuit card 10and the upper side of the mother card 4. The inner leg 38 of eachcontact tongue 36 has an upper side formed with a contact boss 48,making contact with the grounding part of the sender/receiver printedcircuit card 10. The outer leg 40 makes contact with the grounding partof the mother card 4. In FIGS. 4 and 5 the earlier mentioned innermetallic layer of the card 10 is indicated at 50, as well as an outercontinuation 52 thereof, that extends outwardly on the edge 28 of thecard 10 to its lower side for forming said grounding part of the card 10there.

In FIGS. 6-10 an embodiment of the connection device 8 is illustratedmore closely with respect to its design and function, which is intendedfor connecting one end of a sheathed opto fibre 60 to the electro-optocomponent enclosed in the housing 6.

The connection device 8 includes, while referring particularly to FIG.7, a retaining sleeve generally designated 62 for a portion of the fibreconnecting to said end of the sheathed opto fibre 60, a supportingstructure, generally designated 64, for the retaining sleeve 62 intendedto be fixed with respect to the electro-opto component in a way to bedisclosed more closely below, and a spring 66 acting between theretaining sleeve 62 and the supporting structure 64. More particularly,the spring 66 shall, at connection to the electro-opto component in thehousing 6, compensate for tolerances in the length direction of theretaining sleeve 62 with respect to the electro-opto component.

In a way to be described more closely below, the spring 66 and thesupporting structure 64 are mutually shaped to first admit introductionof the retaining sleeve 62 with the sheathed fibre 60 kept thereby inthe direction of the arrow 68, before the spring 66 which may thereuponbe introduced in the direction of the arrow 70 and according to thedashed lines 72 and 74 sidewardly in the supporting structure.

The spring 66 is made in one piece of two spring legs 76 and 78 bentinto a V-shape and arranged in parallel with and joined together at theend of the leg of the respective V by means of ties 80 and 82,respectively. On location in the supporting structure 64 the spring 66straddles the retaining sleeve 62 with the V-shaped spring legs 76 and78 on each side thereof and commonly acting between an abutment 84 onthe sleeve 62 extending around the circumference of the sleeve 62, andan abutment 86 in the support structure.

The support structure 64 is essentially cage shaped and comprises, whilereferring to FIGS. 7-9, a passage for the retaining sleeve 62 extendingin the direction of the arrow 68. This passage includes in turn, in thedirection of the arrow 68, an opening 88 located in an end wall 90, anopening 92 located in an intermediate wall 94, and an end opening 96,that is located at the other end of the supporting structure 64 withrespect to the end wall 90. The end wall 90 and the intermediate wall 94delimit each an upper edge, as seen in FIGS. 7 and 9, together withsidewalls 98 and 100 extending therebetween, a rectangular side openingtowards said passage for introducing the spring 66 in the direction ofthe arrow 70. As appears from FIG. 9 the abutment 86 is located in thisside opening on the side of the end wall 90 facing the side opening.

When located in the supporting structure 64, the spring 66 is kept inplace by the edge of the V of the respective V-shaped spring parts 76and 78 snapping under the free end 102 and 104, respectively, of each atongue 106 and 108, respectively, formed in each one of the side walls98 and 100, respectively. The legs of the spring parts 76 and 78 facingthe wall 94 then abut the abutment 84 of the sleeve 62 on each side ofthe sleeve, and the tie 82 of the spring 66 abuts the abutment 86. Theabutment 84, which accordingly is located between the walls 90 and 94,forms one side of a radial extension from the sleeve, the other side 110of which by engagement with the intermediate wall 94 delimiting movementof the sleeve 62 in the direction of the arrow 68. Movement of thesleeve 62 in the other direction is limited by the engagement of thespring 66 therewith. In FIG. 10 the locations for the abutment 86 andthe intermediate wall 94 with respect to the sleeve 94 are indicatedwhen the sleeve is in its mounted position in the supporting structure64.

Further referring to FIG. 10, the sleeve is assembled, in the shownembodiment, of two mutually concentric parts, viz. a fibre keeping part112 and a fibre guiding in part 114. The parts 112 and 114 are bothessentially bottle shaped with a neck portion 116 and 118, respectively,and a mantle portion 120 and 122, respectively, with open bottom, themantle portion 122 carrying the radial extension 84/110. The mantleportion 120 furthermore is surrounded by a collar 124 extendingoutwardly from its bottom edge and being essentially of the same lengthas the mantle portion 120 and extending parallel with this so that theydelimit a gap 126 between them, the width of which is somewhat greaterthan the thickness of the mantle portion 122 of the part 114. The parts112 and 114 are interconnected with the open end portion of the mantleportion 122 extending into the gap 126.

The neck portion 116 of the part 112 serves for clampingly keeping inplace the sheathed fibre 60, not shown in FIG. 10, that extends up tothe mouth 128 of the neck portion 118. The mouth 128 has a widthcorresponding to the thickness of the optofibre without sheath.

At mounting the sleeve 62 with the sheathed optofibre 60 sitting fixedlytherein, first pulling of a suitable length of the sheathed optofibrethrough the neck portion 116 and clamping of it in the neck portion 116by means of a suitable clamping tool is performed. Thereupon the part ofthe optofibre extending out of the neck portion 116 is cut to a lengththat is greater than the distance between the outer ends of the neckportions 116 and 118 when the sleeve 62 is ready-assembled. Thereuponthe end of the optofibre is uncovered by removing a suitable length ofits mantle, glue is applied on a portion of the end of the mantleportion 122 turned away from its neck portion 118, and this end isintroduced into the gap 126 to the bottom thereof. This is done whilesimultaneously securing that the uncovered fibre end is guided into themouth 128 so that it will at last protrude therefrom. The end thusprotruding is then cut along the end surface of the neck portion 118.

A conceivable and advantageous alternative to the embodiment of thesleeve 62 shown in FIG. 10 and described above, is that the part 114 isreplaced by a layer directly sprayed onto the part 112 and the sheathedoptofibre clamped therein and having the same contours as the part 122when required. The part 112 is then suitably modified so that the collar124 disappears.

The parts 62-66 are dimensioned and mutually shaped in a way that intheir ready-assembled state the support structure 64 surrounds thesleeve 62 essentially over a portion thereof that extends from the rearend of the sleeve 62 up to the transition between the mantle portion 122and the neck portion 118.

The parts 62-66 are enclosed in an outer housing with a pipe socket 130united therewith into one piece, via which the sheathed optofibre 60 isguided into the sleeve 62. The housing is shown in FIG. 7 as dividedinto an upper housing half 132 and a lower housing half 134, which inFIG. 6 are shown in a state mounted by means of screw connections 136and 138. In FIGS. 1 and 2 the same view of the connecting device 8 isshown as in FIG. 6. At 140 and 142 ears extending from each of thehousing halves 132 and 134, respectively, are shown containing screwholes. Referring also to FIGS. 1 and 2 the upper part 18 and the lowerpart 16 of the housing 2 have correspondingly extending ears 144 and146, respectively, provided with screw holes. The ears 140 and 144provided with holes with a screw passing therethrough, on the one hand,and the ears 142 and 146 provided with holes with a screw passingtherethrough, on the other hand, each form a screw joint for joining,according to the dashed lines 148 and 150, respectively, the contactdevice 8 with the housing 2, with the housing 130/132 guided into theguiding-in part 9. In this position the mouth 128 of the sleeve 62 inthe housing 6 is in a correct position with respect to the electro-opticcomponent enclosed therein. The receiving tube 7 then extends into thesupport structure 64 approximately up to its intermediate wall 94,tolerances of the retaining sleeve 62 in its length direction withrespect to the electro-optic component being taken up by the spring 66.

What is claimed is:
 1. An arrangement in an electro-optic circuit thatincludes optical sender components for transforming an electrical outputsignal to an outgoing optical signal and optical receiver components fortransforming a received optical signal to an electrical input signal,connection means for an optical conductor on which the outgoing andreceived optical signals are transmitted, a sender for the electricaloutput signal, and a receiver for the electrical input signal, thearrangement comprising:a module with an electromagnetically shieldedhousing that contains the optical sender and receiver components and theconnection means, and a two-sided printed circuit arrangement that islocated between a lower portion and an upper portion of the housing andthat carries the sender and the receiver on one side each shielded fromeach other by an electrically conducting shielding that is in connectionwith the housing for forming three Faraday's cages, one for the sender,one for the receiver and one formed of the housing in its entirety; andcontact means between the housing and grounding portions of the printedcircuit card arrangement, the shielding between the sender and thereceiver, and an outer printed circuit card on which the module isattachable, wherein the contact means comprises a number of longitudinalspring means along insides of the housing lower and upper portions, andeach spring means is shaped in one piece and has a number of contactpoints for the printed circuit card arrangement, a number of contactpoints for the lower portion, a number of contact points for the upperportion, and a number of contact points for the outer printed circuitcard.
 2. The arrangement of claim 1, wherein each spring means hasafirst web portion that extends along a longitudinal direction of thespring means between the inside of a round about extending side wall ofthe lower portion and a side edge, facing this side wall, of the printedcircuit card arrangement, a second web portion that extends between theoutside of the side wall of the lower portion and the inside of a roundabout extending side wall of the upper portion, first contact tonguesbent away from an upper edge of the second web portion for contact withthe outside of the side wall of the lower portion, second contacttongues bent away from an upper edge of the first web portion forcontact with the inside of the side wall of the upper portion, and thirdcontact tongues, extending between and abutting the grounding portionsof the printed circuit card arrangement and the outer printed circuitcard.
 3. The arrangement of claim 1, wherein the first and second webportions are interconnected by arcuate connection pieces extending overthe side wall of the lower portion, and a first and a second contacttongue are pairwise arranged in spaces between the connection pieces. 4.The arrangement of claim 1, wherein each of the third contact tongueshas an inner leg bent away from the first web portion in between theprinted circuit card arrangement and the outer printed circuit card, andan upper side of which is shaped for contact with the grounding portionof the printed circuit card arrangement, and an outer leg that is bentaway from the inner leg under an acute angle in direction towards theouter printed circuit card for making contact with the grounding portionthereof.